Product Overview
The THINKTANK TT-AHN42F / WAHN42F Series is a parallel backflow safety valve designed specifically for liquid backflow pipelines at the outlet of LPG storage tank pumps.
The listed models include AHN42F-P18 and WAHN42F-P18, with nominal sizes from DN40 to DN100.
When pressure in the pump system exceeds the specified set pressure, the valve opens automatically and allows liquid to return through the backflow line. This helps prevent excessive pressure in the pump outlet piping and supports safe operation of the LPG pumping system.
After system pressure returns to the required level, the valve recloses automatically.
Model Configuration
The product data lists the following two model configurations:
- AHN42F-P18
- WAHN42F-P18
Both are specified for liquid backflow pipelines at the outlet of LPG storage tank pumps.
The provided product data does not define the construction or material difference between AHN42F-P18 and WAHN42F-P18. The appropriate configuration should therefore be confirmed according to the project specification and required valve materials.
Quick Specifications
| Parameter | Specification |
|---|---|
| Model Family | TT-AHN42F / WAHN42F |
| Listed Models | AHN42F-P18 / WAHN42F-P18 |
| Product Type | LPG Backflow Safety Valve |
| Configuration | Parallel Type |
| Size Range | DN40–DN100 |
| Connection | Flanged |
| Application | LPG storage tank pump outlet liquid backflow pipeline |
| Operating Principle | Automatic spring-loaded pressure relief / backflow |
| Function | Pump and piping overpressure protection |
| Manufacturer | THINKTANK |
How It Works
The TT-AHN42F / WAHN42F provides automatic pressure protection by allowing liquid to return through a dedicated backflow line when system pressure becomes excessive.
During normal operation, spring force keeps the valve closed.
When pressure in the protected pump or piping system reaches the specified set pressure, the hydraulic force acting on the valve closing element overcomes the spring force and causes the valve to open.
LPG liquid is then redirected through the return line, reducing pressure in the pump outlet system.
When pressure falls back to the required level, spring force returns the valve to the closed position.
This automatic operating cycle helps protect the pump, piping and associated LPG equipment against excessive pressure.
LPG Pump Backflow Application
The primary application of the TT-AHN42F / WAHN42F is the liquid return line associated with an LPG storage tank pump.
In this type of installation, the valve provides an automatic bypass path when pressure exceeds the specified setting.
The valve can therefore help:
- Prevent excessive pressure in the pump outlet line
- Provide an automatic liquid return path
- Protect associated equipment and piping
- Maintain safer pump operation during abnormal pressure conditions
The return piping arrangement should be considered as part of the overall valve selection and system design.
Typical Applications
The TT-AHN42F / WAHN42F Series can be considered for:
- LPG storage tank pump systems
- LPG pump outlet piping
- LPG liquid return lines
- LPG transfer systems
- LPG storage installations
- Packaged LPG pumping equipment
- Skid-mounted LPG systems
- Liquid bypass and backflow pressure-protection applications
Final valve selection should consider the actual LPG service conditions, set pressure, operating pressure, required return capacity and piping arrangement.
General Performance Requirements
| Applicable Medium | Shell Test Pressure Ps | Seal Test Pressure Pm | Blowdown ΔP | Discharge Pressure Pp | Lift Height H |
| Steam | — | 90% Pk or the minimum reseating pressure, whichever is lower | When Pk ≤ 0.4 MPa: ΔP ≤ 0.04 MPa; when Pk > 0.4 MPa: ΔP ≤ 10% Pk | ≤ 1.03 Pk | Full-lift: ≥ 1/4 d₀; Low-lift: ≥ 1/20 d₀ |
| Air or other gases | 1.5 PN | When Pk ≤ 0.3 MPa: Pm = Pk − 0.03 MPa; when Pk > 0.3 MPa: Pm = 90% Pk | When Pk ≤ 0.2 MPa: ΔP ≤ 0.03 MPa; when Pk > 0.2 MPa: ΔP ≤ 15% Pk | ≤ 1.1 Pk | Full-lift: ≥ 1/4 d₀; Low-lift: ≥ 1/20 d₀ |
| Water or other liquids | — | When Pk ≤ 0.3 MPa: Pm = Pk − 0.06 MPa; when Pk > 0.3 MPa: Pm = 80% Pk | When Pk ≤ 0.3 MPa: ΔP ≤ 0.06 MPa; when Pk > 0.3 MPa: ΔP ≤ 20% Pk | ≤ 1.2 Pk | Full-lift: ≥ 1/4 d₀; Low-lift: ≥ 1/20 d₀ |
Notes:
- Pk = Set pressure
- d₀ = Orifice diameter
- PN = Nominal pressure
- Actual test and performance requirements shall be confirmed according to the selected valve model, project specification and applicable standard.
- For this LPG liquid backflow application, the liquid-service performance requirements are the relevant reference conditions.
Dimensions
| DN | D (mm) | K (mm) | G₁ (mm) | B (mm) | Z₁–φd | L (mm) | H Approx. (mm) |
| 40 | 150 | 110 | 85 | 16 | 4-18 | 200 | 346 |
| 50 | 160 | 125 | 100 | 16 | 4-18 | 230 | 346 |
| 65 | 180 | 145 | 120 | 20 | 4-18 | 290 | 440 |
| 80 | 195 | 160 | 135 | 20 | 8-18 | 310 | 540 |
| 100 | 215 | 180 | 155 | 22 | 8-18 | 350 | 570 |
Dimensions are for preliminary engineering and layout reference. Final approved dimensional drawings should be confirmed before piping fabrication or installation.
Safety Valve Sizing and Selection
For correct selection of the TT-AHN42F / WAHN42F Series, provide:
- LPG service conditions
- Required model or material configuration
- Set pressure
- Pump discharge pressure
- Normal operating pressure
- Design pressure
- Operating temperature
- Required liquid return or bypass capacity
- Valve DN
- Return-line size
- Required materials
- Pump operating conditions
- Storage tank and return piping arrangement
- Applicable project standards or certification requirements
For this type of valve, the required backflow capacity and pump operating conditions are particularly important, because the valve must provide sufficient liquid return capacity when the specified pressure is reached.
Engineering Support
THINKTANK supports LPG storage system integrators, pump skid manufacturers, EPC contractors and industrial users with:
- LPG backflow safety valve selection
- Pump bypass and return valve sizing
- Set-pressure configuration
- Required return-capacity review
- Material selection
- Dimensional drawings
- 3D models for system integration
- Existing valve replacement evaluation
- Project-specific technical documentation
With more than 30 years of industrial valve application experience, THINKTANK can support LPG storage, transfer and pumping projects with application-specific valve selection and equivalent replacement solutions.
